The following error message –


“Duplicate Document Number Error: You must specify a different number. This number has already been used”.



Will appear on your Export to GL tab if a duplicate check number is entered in the check number field in EZLynx that has already been used in QuickBooks Online. 


To resolve this:

  • Turn off the setting in QuickBooks Online.
    • Navigate to Settings.
    • Click Account and Settings.
    • Select Advanced.
    • Under Other Preferences- Select "Warn if Duplicate Check Number is Used".



  • Remove the Check Reference Number in QuickBooks Online.
    • Locate the Check in QuickBooks.
    • Select View/Edit.
    • Remove the Check no.
    • Click Save.


EZTip: Do not delete the journal entry, just remove the check number itself.

  • Reprocess the Transaction in Exports.
    • In EZLynx - Click on the Accounting Icon.
    • Select General Ledger.
    • Click on the "Export to GL" tab.
    • Under the Errors - Select "Reprocess" on all transactions.


Once the QuickBooks online setting for "Warn if duplicate check number is used", is turned off, and the transactions are reprocessed - Then the issue will be fixed moving forward.